Neurons burdened by DNA double strand breaks incite microglia activation through antiviral-like signaling in neurodegeneration

Abstract

DNA double strand breaks (DSBs) are linked to aging, neurodegeneration, and senescence. However, the role played by neurons burdened with DSBs in disease-associated neuroinflammation is not well understood. Here, we isolate neurons harboring DSBs from the CK-p25 mouse model of neurodegeneration through fluorescence-activated nuclei sorting (FANS), and characterize their transcriptomes using single-nucleus, bulk, and spatial sequencing techniques. We find that neurons harboring DSBs enter a late-stage DNA damage response marked by the activation of senescent and antiviral-like immune pathways. We identify the NFkB transcription factor as a master regulator of immune gene expression in DSB-bearing neurons, and find that the expression of cytokines like Cxcl10 and Ccl2 develop in DSB-bearing neurons before glial cell types. Alzheimers Disease pathology is significantly associated with immune activation in excitatory neurons, and direct purification of DSB-bearing neurons from Alzheimers Disease brain tissue further validates immune gene upregulation. Spatial transcriptomics reveal that regions of brain tissue dense with DSB-bearing neurons also harbor signatures of inflammatory microglia, which is ameliorated by NFkB knock down in neurons. Inhibition of NFkB or depletion of Ccl2 and Cxcl10 in DSB-bearing neurons also reduces microglial activation in organotypic brain slice culture. In conclusion, we find that in the context of age-associated neurodegenerative disease, DSBs activate immune pathways in neurons, which in turn adopt a senescence associated secretory phenotype to elicit microglia activation. These findings highlight a novel role for neurons in the mechanism of age-associated neuroinflammation.

Tau polarizes an aging transcriptional signature to excitatory neurons and glia

“…Knockdown of Rel in Drosophila neurons promotes survival (Kounatidis et al, 2017), whereas activation of the Rel signaling pathway leads to neurodegeneration (Cao et al, 2013). Consistent with our results, a recent re-analysis of snRNAseq data from Mathys et al (2019) revealed AD-associated perturbation of NFκB immune pathways in excitatory neurons, possibly triggered by DNA double strand breaks (Welch et al, 2022).…”

“…Overall, our results suggest that besides the well-established requirements in glia (see below), innate immune response pathways may also have important, cell autonomous roles in modulating neuronal vulnerability to tau pathology in AD. Indeed, both insect and mammalian neurons express evolutionary-conserved innate immune signaling pathways, including Toll-like receptors and NFκB signal transduction components, and these pathways can be triggered by infection or other cellular insults (Lehnardt et al, 2003;Tang et al, 2007;Cao et al, 2013;Cho et al, 2013;Welch et al, 2022). In addition, NFκB immune signaling pathways have been coopted for diverse, non-canonical functions, such as in neurodevelopment and synaptic plasticity (Okun et al, 2011;Gutierrez and Davies, 2011;Nguyen et al, 2020).…”

Senescence of cortical neurons following persistent DNA double-strand breaks induces cerebrovascular lesions

“…Genome instability with increased DNA double strand breaks (DSBs) is detrimental to neurons of the brain and has been implicated in diverse neurodegenerative disorders (NDs) [1][2][3][4][5][6] . However, the etiology of NDs is multifaceted, the progressive decline in number and activity of neurons exhibits significant comorbidity with glial and cerebrovascular abnormalities [7][8][9][10] .…”